Motion is still an unsolved problem in magnetic resonance (MR) imaging and is a dominant source of artifacts. Motion often results in prolonged or diagnostically inadequate studies. This can lead to considerably lower diagnostic confidence or even incorrect diagnoses. To overcome motion, sedation or general anesthesia are sometimes required, which can add extra risk factors to the procedure. Moreover, the decreased patient comfort and throughput is inconvenient for both the patient and the clinicians, and can add significantly to overall exam/health care costs. Providing an accurate and reliable 3D motion tracking device is key for many prospective or retrospective motion correction approaches.
One approach for MR motion tracking that has been considered in the art is the use of wireless markers as fiducials for motion tracking, e.g., as considered by Flask et al. (JMRI 14:617-627, 2001). In such approaches there are several markers each providing signals to a common output (e.g., the MR receive coils), and it is necessary to determine the correspondence between markers and marker signals in order to use the markers for motion tracking. Various approaches for this have been considered in the art, such as tomographic reconstruction, but the correspondence problem remains a source of difficulty for conventional motion tracking with wireless markers.